Area Code 4284 – Tachikawa, Tokyo

Geographic Coverage and Administrative Jurisdiction

The +81 4284 area code serves the western Tokyo region, specifically the city of Tachikawa and its surrounding areas. Tachikawa is a major commercial and administrative hub within the Tokyo Metropolis, located approximately 40 kilometers west of central Tokyo. The code 4284 is part of the larger 042 area code group, which covers multiple cities in western Tokyo, including Hino, Kokubunji, and Kunitachi. However, 4284 is specifically allocated to Tachikawa and its immediate vicinity, ensuring efficient call routing within this densely populated urban area.

Dialing Formats and Caller Instructions

For local callers within Japan, the area code 4284 is dialed with a leading zero: 04284. The full local number consists of the area code (without the zero) plus the subscriber number, which typically has 6 to 7 digits. Thus, a complete local number appears as 04284-X-XXXX or 04284-XX-XXXX, depending on the subscriber line length.

When calling from outside Japan, international callers must use the country code +81, followed by the area code without the leading zero, and then the subscriber number. For example, to call a Tachikawa number, one would dial +81 4284 X-XXXX (omitting the zero). This format is compliant with ITU-T E.164 international numbering standards.

Overlay and Numbering Plan Considerations

Currently, the 042 area code group, including 4284, does not have an overlay code. This means that local calls within the same area code do not require an additional area code prefix. However, as Tokyo’s western suburbs continue to grow, the Ministry of Internal Affairs and Communications (MIC) may introduce overlays in the future to meet demand. Subscribers should be aware that if an overlay is introduced, local dialing patterns may change, requiring 10-digit dialing for all calls within the region.

Services and Usage

The 4284 area code is used for fixed-line telephone services, including PSTN and VoIP services that are geographically anchored. Businesses and residents in Tachikawa rely on this code for reliable voice communication. The area is home to several government offices, corporate headquarters, and the Tachikawa Air Base, which contributes to a mix of residential and commercial telephony needs.

For callers from other parts of Japan, dialing 04284 from outside the region requires the full national trunk prefix (0) and area code. For international callers, the +81 country code is essential. Always verify the subscriber number length before dialing to ensure accurate call completion.